1. Field of the Invention
The present invention relates to an optical disc cartridge or caddy and more particularly relates to an optical disc cartridge or caddy which protects the disc stored therein from ambient light.
2. Discussion of the Background
A conventional optical disc cartridge or caddy 1 is shown in FIGS. 7 and 8 and corresponds to the optical disc cartridge of Japanese Utility Model No. 1-93674 (1989) which is incorporated herein by reference. This disc cartridge has become a defacto standard for CD-ROMs and was developed by Sony. The optical disc cartridge 1 includes a box-shaped body 3a for holding an optical disc 2. The disc cartridge includes a cover 3b which opens in order to insert and remove the optical disc 2. The cover 3a pivots on hinges 8. In the center of the inner side of the cover 3b, there is a rotatable clamper 4 which clamps the optical disc 2 to a disc driving device (not shown) in an optical disc recording/reproducing apparatus. The cartridge body 3a includes an opening 5 used by an optical head to access the disc 2 through a slidably mounted shutter 6 which opens and closes the opening 5.
The optical disc 2 may be a CD-ROM which is a read only memory used exclusively for playing pre-recorded information or a CD-R which is a recordable compact disc used to store information specified by a user and which is retrievable by a user. For a conventional CD-ROM, one side of the disc 2 will be a label 2a containing printed information such as the letters “ABCDE” illustrated in FIG. 7. The bottom side of the disc 2 is used to store information readable by a CD reader or player. The outer edge of the disc is designated by 2b. The cover 3b of the optical disc cartridge or caddy is a transparent material which allows a user to see the information 2a on the disc, even when the disc is in the cartridge 1 and the cover 3b of the cartridge is closed.
Information is stored on CD-ROMs as convex indentations known as pits, or concave protrusions. Generally speaking, these concave and convex portions of the disc do not deteriorate due to exposure to light. However, for recordable compact discs (CD-Rs), as the disc has information recorded thereon by a laser in a recording/reproducing apparatus, for example a laser beam with a wavelength of 780 nanometers and a power of 5 to 10 milliwatts, information on the disc can be deteriorated or destroyed by exposure to light. In order to read the disc, a laser having a wavelength of 780 nanometers using a power of 0.5 milliwatts is typically used.
The present inventor has realized that if a CD-R is placed in a cartridge having a transparent cover and exposed to light, information on the disc may be deteriorated or destroyed.